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Determination of trace concentration of ammonia in the atmosphere using pyridine-pyrazolone reagent
495
Discussions
SURVEY AND ANALYSIS OF HALOCARBONS IN THE ATMOSPHERE BY GAS CHROMATOGRAPHY-MASS SPECTROMETRY* In their paper Grimsrud and Rasmussen give important new data for the contribution of halocarbons to the haloacne uarticuiarly the chlorine budget. This is especially &e fdr their da& on Chloro~uorme~hane 11and 12 which * Grimsrud E. P. and Rasmussen R. A. (1971) Atmospherie Encironmeftt 9, told-1017.
DETERMINATION OF TRACE CONCE~RATION OF AMMONIA IN THE ATMOSPHERE USING PYRIDINE-PYRAZOLONE REAGENT* In the above article. Okita and Kanamori reported that impinger collection systems using 0.02 N H,SO, to collect atmospheric ammonia were very inefficient. Their data show that, after sampling was continued for various lengths of time (dependent upon NH3 concentrations), the collection efficiency tended to decrease. Furthermore, their efficiency studies using three impingers in series showed that ammonia was present in the second- and third-position impingers. thereby indicating a poor collection effciency. initially our laboratory work tended to show similar results, although data were not consistent. Further investigation into the technique led to the discover! that the poor reproducibility of the samplin? method and the “poor efficiency” were both due to contamination of the sampling equipment. The bubbler (Axelrod et al., 1971) and the other equipment were all cleaned in an alkaline solution of Contrad 70” (Harleco, Philadelphia. PA) maintained at 50-70X * Okita T. and Kanamori S. (1971) Atmospheric
Enriron-
ment 5. 621-627.
indicate up to twice the value as those pre\iouslp obtained by gas chromatography. It is an old ruie in analkticdl chemistry that an! data become only reliable if at least obtained b) two independent methods. These CFbI concentrations may imply that there is more in the atmosphere than released by man-certainly a most startling implication considering the CFM-problem. This implication should prompt very careful checks and crosschecks between the analytical methods presently in use to insure that further compilation of data is beyond doubt. .tfa.~-Planck-fnsritrrt fiir Chrmir (Otto-Hahn-lnstirut), Post$ach 3060. D-65 Main:, Germany
and the required pH. The equipment was thoroughI!. washed in deionized water and was used immediately. The bubblers were filled with 13 cm’ 0.01 N HISO, and samples were taken at 2.0 I min-‘. A Nuclepore I !tm prefilter was used throughout. Solution that evaporated from the bubblers was replaced with deionized water. The analysis was carried out according to an indophenol procedure adapted from Harwood and Kuhn (1970). The solutions used in the analysis were the followin_f: trisodium phospate buffer (Na,PO,* llW,O)-ll”, w/v III deionized water: phenol stock solution-340g phenol dissolved in absolute methanol to a final volume of 500 cm’: phenate reagent A-O.I g sodium nitroprusside dissolved in 15 cm3 deionized water. to which was added 75 cm’ phenol stock. with the solution then being diluted to 100 cm3 total with deionized water: reagent B-1 1.5 cm3 commercial bleach (Xi, Cl) and 20 cm3 5 M XaOH diiuted to 100 cm3 with deionized water. To the bubblers were added. in order. 6 cm3 trisodium phosphate buffer. I cm’ phenate reagent A. then 5 cm’ reagent B. Thirty minutes were allowed for color development and the samples were measured for absorbance at 630 nm on a Coleman Model 124 double-beam spectrophotometer. The influence of length of sampling time was studied by sampling -20 ppbv NH, over a I-2 h period. One set of bubblers was used to sample over the entire time period while another set was chang,ed each quarter of the sampling period. As can be seen m Table 1. there was no drop in collection efficiency for bubblers used the entire sampling period. Experiments where two bubblers were
Table 1. Collection efficiency vs sampling time Length of sampling period
Average SH3 concentration for I-quarter-period samples
Average NH, concentration for full-period samples
lh 2h
17.0 ppbv 14.4 ppbv
18.1 ppbv 24.0 ppbv
Table 2. Field data (2 l;min)* Date 1 July 1975 (a.m.)
1 Jufy 1975 (p.m.) 3 July 1975 4 July 1975 8 July 1975
Location
Ammonia concentration (ppbv)
Laboratory Laboratory NCAR RoofWAR Foof NCAR Roof
* Sampling time ranged from 60 to 120 min. t Based upon three samples taken in parallel.
18.6 24.3 4.5 3.s 2.9
O0 SD.+ 0 1 s :
496
Discussions
placed m se&s and 2U ppbv .CH, was sampled at 2 1 min-’ for I h showed no .VH, in the second bubbler. indicating that all of the SH, was captured by the first unit. Table 1 shows data for samples taken in the laboratory room and on the NCAR roof on relatively pollution-free days. The data obtained were quite reproducible with an average percent S.D. of 2,. After our use of the heated Cwtrad 70. we found no pfobiem in obtaining pod data
l Present address: Coors Spectra-Chemical Laboratory, Golden. CO 80401. U.S..-\. t The National Center for Atmospheric Research is sponsored by the National Science Foundation.
through the use of bubbler collection s!,stcms. investigation also showed that at least one other acid. dl-malic acid (O.I”,, w v). gave similarly good collection cfhciencies. H. D.
..iXELROD
J. P. GREWBERG’
REFEREICES
Axeirod H. D.. Wartburg A. F.. Teck R. J. and Lodge J. P.. Jr. ( I?7 I) New bubbler design for atmospheric sampling. &wl,rt. Chefs. 43. 1916--1917. Harrvood J. E. and Kuhn A. L. (1970t A calorimetric method for ammonia in natural uaters. Ctbr. Rrs. 4. 803-S 11.
Discussions
SURVEY AND ANALYSIS OF HALOCARBONS IN THE ATMOSPHERE BY GAS CHROMATOGRAPHY-MASS SPECTROMETRY* In their paper Grimsrud and Rasmussen give important new data for the contribution of halocarbons to the haloacne uarticuiarly the chlorine budget. This is especially &e fdr their da& on Chloro~uorme~hane 11and 12 which * Grimsrud E. P. and Rasmussen R. A. (1971) Atmospherie Encironmeftt 9, told-1017.
DETERMINATION OF TRACE CONCE~RATION OF AMMONIA IN THE ATMOSPHERE USING PYRIDINE-PYRAZOLONE REAGENT* In the above article. Okita and Kanamori reported that impinger collection systems using 0.02 N H,SO, to collect atmospheric ammonia were very inefficient. Their data show that, after sampling was continued for various lengths of time (dependent upon NH3 concentrations), the collection efficiency tended to decrease. Furthermore, their efficiency studies using three impingers in series showed that ammonia was present in the second- and third-position impingers. thereby indicating a poor collection effciency. initially our laboratory work tended to show similar results, although data were not consistent. Further investigation into the technique led to the discover! that the poor reproducibility of the samplin? method and the “poor efficiency” were both due to contamination of the sampling equipment. The bubbler (Axelrod et al., 1971) and the other equipment were all cleaned in an alkaline solution of Contrad 70” (Harleco, Philadelphia. PA) maintained at 50-70X * Okita T. and Kanamori S. (1971) Atmospheric
Enriron-
ment 5. 621-627.
indicate up to twice the value as those pre\iouslp obtained by gas chromatography. It is an old ruie in analkticdl chemistry that an! data become only reliable if at least obtained b) two independent methods. These CFbI concentrations may imply that there is more in the atmosphere than released by man-certainly a most startling implication considering the CFM-problem. This implication should prompt very careful checks and crosschecks between the analytical methods presently in use to insure that further compilation of data is beyond doubt. .tfa.~-Planck-fnsritrrt fiir Chrmir (Otto-Hahn-lnstirut), Post$ach 3060. D-65 Main:, Germany
and the required pH. The equipment was thoroughI!. washed in deionized water and was used immediately. The bubblers were filled with 13 cm’ 0.01 N HISO, and samples were taken at 2.0 I min-‘. A Nuclepore I !tm prefilter was used throughout. Solution that evaporated from the bubblers was replaced with deionized water. The analysis was carried out according to an indophenol procedure adapted from Harwood and Kuhn (1970). The solutions used in the analysis were the followin_f: trisodium phospate buffer (Na,PO,* llW,O)-ll”, w/v III deionized water: phenol stock solution-340g phenol dissolved in absolute methanol to a final volume of 500 cm’: phenate reagent A-O.I g sodium nitroprusside dissolved in 15 cm3 deionized water. to which was added 75 cm’ phenol stock. with the solution then being diluted to 100 cm3 total with deionized water: reagent B-1 1.5 cm3 commercial bleach (Xi, Cl) and 20 cm3 5 M XaOH diiuted to 100 cm3 with deionized water. To the bubblers were added. in order. 6 cm3 trisodium phosphate buffer. I cm’ phenate reagent A. then 5 cm’ reagent B. Thirty minutes were allowed for color development and the samples were measured for absorbance at 630 nm on a Coleman Model 124 double-beam spectrophotometer. The influence of length of sampling time was studied by sampling -20 ppbv NH, over a I-2 h period. One set of bubblers was used to sample over the entire time period while another set was chang,ed each quarter of the sampling period. As can be seen m Table 1. there was no drop in collection efficiency for bubblers used the entire sampling period. Experiments where two bubblers were
Table 1. Collection efficiency vs sampling time Length of sampling period
Average SH3 concentration for I-quarter-period samples
Average NH, concentration for full-period samples
lh 2h
17.0 ppbv 14.4 ppbv
18.1 ppbv 24.0 ppbv
Table 2. Field data (2 l;min)* Date 1 July 1975 (a.m.)
1 Jufy 1975 (p.m.) 3 July 1975 4 July 1975 8 July 1975
Location
Ammonia concentration (ppbv)
Laboratory Laboratory NCAR RoofWAR Foof NCAR Roof
* Sampling time ranged from 60 to 120 min. t Based upon three samples taken in parallel.
18.6 24.3 4.5 3.s 2.9
O0 SD.+ 0 1 s :
496
Discussions
placed m se&s and 2U ppbv .CH, was sampled at 2 1 min-’ for I h showed no .VH, in the second bubbler. indicating that all of the SH, was captured by the first unit. Table 1 shows data for samples taken in the laboratory room and on the NCAR roof on relatively pollution-free days. The data obtained were quite reproducible with an average percent S.D. of 2,. After our use of the heated Cwtrad 70. we found no pfobiem in obtaining pod data
l Present address: Coors Spectra-Chemical Laboratory, Golden. CO 80401. U.S..-\. t The National Center for Atmospheric Research is sponsored by the National Science Foundation.
through the use of bubbler collection s!,stcms. investigation also showed that at least one other acid. dl-malic acid (O.I”,, w v). gave similarly good collection cfhciencies. H. D.
..iXELROD
J. P. GREWBERG’
REFEREICES
Axeirod H. D.. Wartburg A. F.. Teck R. J. and Lodge J. P.. Jr. ( I?7 I) New bubbler design for atmospheric sampling. &wl,rt. Chefs. 43. 1916--1917. Harrvood J. E. and Kuhn A. L. (1970t A calorimetric method for ammonia in natural uaters. Ctbr. Rrs. 4. 803-S 11.